Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$98.48	10.283%	$108.6067	$108.61	$108.60	$108.60
Purchase #2	$153.65	5.561%	$162.1945	$162.19	$162.20	$162.20
Purchase #3	$158.47	8.721%	$172.2902	$172.29	$172.30	$172.30
Purchase #4	$145.51	6.412%	$154.8401	$154.84	$154.85	$154.80
Purchase #5	$155.89	11.326%	$173.5461	$173.55	$173.55	$173.50
Purchase #6	$177.57	10.522%	$196.2539	$196.25	$196.25	$196.30
Purchase #7	$226.39	12.585%	$254.8812	$254.88	$254.90	$254.90
7 purchase totals =	$1,115.96		$1,222.6127	$1,222.61	$1,222.65	$1,222.60